Human Evolution ANT 152
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This 9 page Class Notes was uploaded by Emelie Kihn on Tuesday September 8, 2015. The Class Notes belongs to ANT 152 at University of California - Davis taught by H. McHenry in Fall. Since its upload, it has received 41 views. For similar materials see /class/187697/ant-152-university-of-california-davis in anthropology, evolution, sphr at University of California - Davis.
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Date Created: 09/08/15
Overview of the processes of organic How do the pieces t together Today a framework for understanding the mechanisms by which evolutionary change occurs Anthropology 152 Lecture 3 Evolutionary Processes and Patterns The modern understanding oforganic evolution began in 1859 with the publication ofOn t Origin ofSpecies by Charles Darwin 39 9 39m Before Darwin m w u species did not evolve Aristotle was a great naturalist but he always maintained the immutability of species Immutabxhty of 7 sp spies Genesis was taken very literally so that out the exact 39 quot day of creation The prevailing interpretation of Genesis to have been was that life was created in 6 days with 4004 B C the Earth on the rst day vegetation on 39 39 the third aquatic life on the lth and Ill lI II II Al Western view of time was very shortsighted Elsewhere there were notions 2 more like those oftoday or example ancient Indian scholars a a much vaster View oftime involving millions of years a kalpaquot l l Much of modern science grew out of the the Western tradition especially during the 18m and 19th Centuries when Europeans began to explore the rest of the world and the Industrial Revolution moved the earth and revealed fossils Fossils gave visions of a world long vanished One attem pt to reconcile fossils with dominant interpretation of Swingingquot 1832 who proposed a theory called catastrophism fossils were laid down during a series of great earth upheavals Lamarck 1744 1829 proposed that life evolved but the mechanism he championed is now discredited the inheritance of uired characteristics Charles Darwin 18091882 studied to become a doctor then a minister but he preferred natural history Iquot ln1831 he joined a ve year expedition on the HMS Beagle as a naturalist r V In 1838 Darwin read Malthus about the tendency for over 3 population This spurred him to sketch his theory of evolution by natural selection Darwin did not publish the theory until 1859 Wallace came up with the same theory in 1858 Wallace and DanNin presented their theory at a meeting in 1858 DanNin finally started working on the book and in 1859 it appeared Origin of Species 1859 was a great turning point in our understanding m quotu 5 n MIHJJ HIJ39III39f It proved to most that evolution did happen It also provided a mechanism natural selection that after many decades finally became the core of the modern theory of evolution TIM illlll39rlN ill l39l l39lli IP quotH Hill quot IIlU I h II l DanNin39s theory did not include a proper explanation of three things mechanism of inheritance source of variation mechanism of speciation Why didn tI think of that 4 w hequot If only DanNin had known about the work of Gregor Mendel he might have given us a more complete theory 5 H E If u inhibit ii History of Evolutionary Ideas Mendel s work was rediscovered in 1900 however early Mendelians initially rejected Darwin s ideas In 1937 Dobzhansky integrated it with Darwin s ideas in the Modern Synthesis The current understanding ofthe s tIct eory of evolution is complicated and subtle One attempt to classify the major evolutionary processes Enders and McLellan 1988 me u with 6 processes For our purposes we will look at 3 fundamental phases production of genetic variation via mutation and other genetic processes reduction ofthis variation prim arin by natural selection pecies formation by reproductive isolation Production of genetic variation In this class we will not go into the processes that create genetic variation except to note that they are random with respect to the direction of evolution Ultimately new genetic variation is produced by chemical changes in the DNA ie mutations Mutation rate has little relation to evolutionary rate in complex organisms like mammals Reduction of genetic variation occurs primarily by natural selection although redu tion can also occur by generic drift which is variation is lost by chance in small populations Natural selection shapes the genetic variation each gener ti n although it operates on phenotypic variation It is the guiding force in evolution but it has no foresight It simply results from the fact that the best adapted variants will tend to leave ore offspring each generation The theory of Natural selection has been pounded on the anvil of doubt by brilliant skeptics for 140 years But its golden core shines brighter today than even It is the core ofthe Synthetic Theory It is Darwin39s great contribution to human understandi of life however painful its implications are for our lives Natural selection acts on the phenoype It is the appearance behavior physiol 09 etc e he hent e that determineswhich organIsms will leave more surviving offs ring But it is only inherited variability ie variability with a genetic component that is passed from one generation to the ne Natural selection was Darwin s great contribution to evolutionary theory He put together 3 observations Tendency tb byenbbbbiate Enbnnity bit natural variability yyitnin species Tendency fur tne best tit ariantstu ieaye rnbre ensuring i L Darwin s 3 observations Tendency to overpopulate n E Q Available fund expands arithmetically 5b pupulatiun is checked by lack uf rESDurEES vi a in Tendency to overpopulate More gametes are produced than can possibly survive For example the female cod lays two million eggs but only two offspring survive to reproduce Population pressure is powerful in humans Earth39s population estimated at 6 billion on Oct 12 1999 Tendency to overpopulate is certainly true of people In 1960 a study derived a formula using the best data possible to predict future population gro h This doomsday equationquot predicted that human population would go to in nity in 2026 And since 1960 we are ahead of schedule The doomsday equation under estimated the actual population growth It predicted 365 billion in 1975 but the actual population was 9 It predicted 397 in 1980 but we reached 44 hen billion byt It predicted 5 billion by 1989 but we passed that number in 1986 Enormity of natural variabiliy within pecie Both phenotype and genot e 40 to 50 of coding loci exist in allelic form Phenotypic variation is what Natural Selection acts on Phenotype is controlled to some degree by the genotype Tendency for the best 39 variants to leave more offspring Most selection is stabilizing It tends to ru e off extremes and ge and Beaks of nches kept at a certain depth each generation by stabilizing 139 selection 934 Directional selection Directional selection changes the variability birds with deeper beaks were less likely to die because they could process large hard seeds The peak ofthe distribution has shifted to V l l l i the right Directional selection Several species ofmoths used to be predominantly pale gray 39 a When countryside was blackened by industrial smoke the frequency of light colored oths decreased and melanized darkened moths became the most frequent Reproductive Isolation The last basic process of evolution the formation of a new species by reproductive Even though Darwin called his classicm Origin of Species he really didn39t develop a good model of how species originate We now recognize that it involves reproductive isolation between members of different species Reproductive isolation Emu t i The diversity of life is packaged in discrete entities calle species Members ofa species are generally similarto other members ofthe same species And different from other species Gorillas and chimps are distinct species Reproductive Isolation A species is a group of interbreeding organisms that are reproductively isolated from other organisms Reproductive isolation eans that members of one species do not produce fertile offspring with members of a different species Members ofa species can interbreed and produce fertile offspring there is no obstruction of gene ow bers ofa s ecies Gene ow maintains similarities among members Reproductive Isolation irnagine a bird speeies living ein an island tnat nas a Wu nabitats Wet i dry Natural selectiun favurs dl ErE lnSIZEd beaks in each habitat Elut birds fly back and furtn and interbreed Tnis gene fluvv swamps divergent Evulutlun Reproductive Isolation tnataretuufarapartfurgene uw Natural seieetien Will lead tn adaptatiunstu tne ieeai Envvunrnents Reproductive Isolation natural SEIEEIIDH EDHIIHUES El result In adaptatiuns El the Intel 5 then thswwv taaiv Reprodu ctive Isolation Arter repruductive iseiating rneenanisrns su tnat even it geegrapnieai ISEIIatIEIri breaks duvvn they Will netrerrn Viable hybrids Reprodu ctive Isolation less Well adapted tn eitner Enwrunment NaturalseiemienWiiiaetagainstinterbreeging Reproductive Isolation There are rnany kind at repruductlve isblating rneehanisrns Eehavlural mallard The processes that produce genetic change generation are part of the study of microevolution ducks and pintail Will hybrldlze in eaptiyity ut nt ating habits keep th rn 3 Macroevolution is the study of changes observed through geological time and deals separate W the Wlld with transspeci c evolution Genetics and ecology deal with microevolutionary processes enetlc tvvu segtlt cells dun t get tugether pruperlyr as seen in the rnule Paleontology and comparative biology deal with macroevolutionary processes Microevolution Darwin said lr it cuuld be dernclnstrated that an i vynlcn cuuld nut pusslbly haye beenfurrned by nurn rubs successlve slight rnbgineatibns rn th y my Bum absumw Mechanisms of Macroevolutlon break duvvn Elutl can flnd nu such case transspeci c evolution is With the nothing but an extrapolation segueneing bit the ehirnp genurne it is and magni cation ofthe events that take place within beebrnlng populations and species 39 lncreaslngly clear that slight alteratluns cmst Mayr Before there was a good Fh fossil record most ykucg39adm39s quot But there are prucesses that evolutionary biologists quot V m W l assumed that change rnacruevulutlun can reveal One isthe rate and pa speeiatibn ln rnclst cases Where there is a guudfussllrecurd the pattern seerns tn be bne pr lung perluds at little change stasls fulluvved by rapld change punctuatlun Y processes called phgdetic gradualism Change occurred gradually a ong branches anagenesis This pattern at lung peribds at little ehange fulluvved b relatively abrupt ehange is called punctuated egulllbrlurn Funmuated Equilibrium Speciatiun uncursprirnaril Wnen srnall peripheral and m r9 new species became Visible in the fussll retard The model of punctuated equilibrium is helpful in understanding the fossil record New species anse uutufsrnall peripheral and isulated pupulatiuns Whatvve sample lrl the fussll reenrd lS mustlythe successful cure er the species Rarely sampled are the srnall lsulated penpnerai pupulatiuns frurn w re enange Will rnust likely an And repruductive isulating mechanisms Will ultimately new Next time Before Hominids 1 The Geologic Time Frame
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